Alboluxin, a snake C-type lectin from Trimeresurus albolabris venom is a potent platelet agonist acting via GPIb and GPVI

Alboluxin, a pozent platelet activator. was purified from Trimeresarus albolabris venom with a mass of 120 kDa non-reduced and, after reduction, subunits of 17 and 24. kDa. alboluxin induced a tyrosine phosphorylation profile in platelets that resembles those produced by collagen and convulxin, involving [he time dependent tyrosine phosphorylation of Fc receptor gamma chain (Fc). phospholipase Cgamma2 (PLCgamma2). LAT and p72(SYK). Antibodies against both GPIb and GPVI inhibited platelet aggregation induced by alboluxin, whereas antibodies against alpha(2)beta(1) had no effect. Inhibition of alpha(IIb)beta(3) reduced the aggregation response to alboluxin, as well as tyrosine phosphorylation of platelet proteins. showing that activation of alpha(IIb)beta(3) and binding of fibrinogen are invoked in alboluxin-induced. platelet aggregation and it is not simply agglutination. N-terminal sequence data front the beta-subunit of alboluxin indicates that it belongs to the snake C-type lectin family. The C-type lectin subunits are larger than usual possibly due to post-translational modifications such as glycosylation. Alboluxin is a hexameric (alphabeta)(3) snake C-type lectin which activates platelets via both GPIb and GPVI.